Numerical and Experimental Investigation of the Addition of Surface Roughness on Micro-Scale Propeller Performance

Micro aerial vehicles (MAVs) require efficient propellers when operating at low Reynolds (Re) numbers due to increased viscous forces. Numerical and experimental methods are combined to show that propellers with surface roughness exhibit enhanced and reduced thrust and power coefficients, respectively, compared to their smooth counterparts. A numerical investigation using an unstructured mesh finite volume flow-solver showed that surface roughness reduces the pressure on the suction side of a propeller's blades, increasing pressure force contributions to its thrust. Further, the decreased pressure contribution to the drag lowers the required torque, yielding a net input power reduction despite an increase in viscous drag. These findings are corroborated by in-house thrust stand-based experiments, which revealed that surface roughness increased and decreased the thrust and power coefficients each, respectively, when compared against a baseline smooth propeller.